How can you measure Earth Fault in an Electrical Circuit ?
Thursday, March 20th, 2008 at
9:58 am
Naughty Nitin asked:
Suppose there is a fault then how will you ensure that there is an earth fault or not.
Tagged with: Earth Fault • Electrical Circuit
Filed under: Engineering
Like this post? Subscribe to my RSS feed and get loads more!
sussex electrics
no connection maybe
sussex electrics
By using some kind of bridges which used to find the earth faults, connect 2 arms with the circuit and then check the balance, some calculations is occurred and then you can know if there is a fault or no.
brighton electrical
Measure current in on the live and out on the neutral – they should be the same. If not, the difference is flowing to earth, probably through a fault (for example through the body of the user of an electrical piece of equipment). This is what earth leakage protectors do ie. if there is a difference (above a predetermined safe limit) the protector shuts down the circuit to prevent damage or injury.
brighton electric
I am having trouble understanding your question, there are two possible answers.
If there is a fault with the Earth then it can be measured using resitometer to meaure the resistance between ground and the earth cable (this should normally be zero)
If you are trying to meaure how much current is being lost to earth then connect an ammeter series with the earth to meaure the current flowing to earth.
Refer to the Institute of Electrical Engineers Onsite Guide for circuit tesing standards if working in the UK.
brighton electric
Unfortunately, there is no practical method of measuring earth faults as the impedance at the point when the earth fault occurs can vary enormously. ie. take the case where a power line falls to ground. It may fall in an area where the soil restistivity is high or low, it could be wet or dry etc. etc etc.
Current flowing to ground (or earth depending in what part of the world you live) depends on the “Fault Level”. Fault level is the maximum available fault current that can flow into a bolted short. (either to ground or between phases). The fault level is determined by the Z% of the transformer feeding the fault however, the level of available fault current at the fault’s location is mitigated by the circuit impedance up to the location.
To summarize…… Current flow into an earth fault has to be calculated rather than measured as the earth fault currents can be as high as 100,000 amperes.
Source: Electrical Engineer with 40 years experience